The invention relates to a method for adjusting the operation of a hydraulically operated boom, the boom comprising at least two mutually movably coupled boom parts, which are coupled movably to rotate about an axis with respect to one another or to move in linear movement by means of a hydraulic actuator,                control means for controlling the hydraulic actuators,        a detector for detecting the movement and position between the boom parts,        each movement being controlled by a joint controller included in the control means and for adjusting the operation of the boom it is possible to configured a movement-specific adjustment parameter of the joint controller in the control means for each particular movement.        
The invention further relates to an apparatus for adjusting the operation of a hydraulically operated boom, the boom comprising at least two mutually movably coupled boom parts, which are coupled movably to rotate about an axis with respect to one another or to move in linear movement by means of a hydraulic actuator, control means for controlling the hydraulic actuators, a detector for detecting the movement and position between the boom parts, each movement being controlled by a joint controller included in the control means and for adjusting the operation of the boom it is possible to configure a movement-specific adjustment parameter of the joint controller in the control means for each particular movement.
The invention still further comprises a computer program for controlling a processing unit comprised by the apparatus performing adjustment of the operation of a hydraulically operated boom, the boom comprising at least two mutually movably coupled boom parts, which are coupled movably to rotate about an axis with respect to one another or to move in linear movement by means of a hydraulic actuator, the apparatus comprising control means for controlling the hydraulic actuators, a detector for detecting the movement and position between the boom parts, each movement being controlled by a joint controller included in the control means and for adjusting the operation of the boom it is possible to configure a movement-specific adjustment parameter of the joint controller in the control means for each particular movement, the computer program comprising program code for adjusting the operation of the boom.
Multijoint, hydraulically operated booms are used in various apparatuses. Hydraulic booms are manipulators of “open chain” type, which consist of more than one successive joints, which are connected by a joint arm. The joints may be rotatable rotation joints or prismatic joints, in which the mutual movement of the joint arms is linear i.e. in a straight line. To achieve a Cartesian position of a boom end the joint angles of boom joints must be brought through adjustment to values calculated by inverse kinematics. Information on the joint positions is obtained by detectors, and the position data produced thereby is applied, when adjusting each joint, to a joint controller adjusting the position of the joint concerned. The joint controller is typically a digital processor application that controls the actuator altering the joint position such that the quantity of difference between the desired joint position and the actual position measured with the detector approaches zero as close as possible.
The object of the boom control is that a tool locating at the boom end is in a desired position with sufficient accuracy. On the other hand, the object is that the dynamic characteristics of the boom movement are as good as possible. Good dynamic characteristics refer to a positioning rate of the joints and thereby of the entire boom to a desired position and to minimum amount of oscillation in the actuators and the adjustable joints.
It is a challenging task in the case of hydraulic booms to tune the joint controller parameters implemented with software or comprised by control equipment such that the employed adjustment algorithm would make the boom behave in a desired manner, i.e. to obey alterations in the set value as faultlessly as possible. Due to the hydraulic boom's complex dynamics that is difficult to model it is challenging to tune the adjusters. In addition, parameter tuning of the joint controllers is challenging, because hydraulic booms are characterized by structural flexibility and elasticity. Optimal tuning of joint controllers differs greatly from the case of one degree of freedom, when it is required that the boom joints move simultaneously. It is difficult, if not outright impossible, to apply common tuning methods to joint controllers of multijoint manipulators. The management of boom control and adjustment is further complicated by the fact that as one joint is adjusted, acceleration and position changes of other joints as well as changes in the moment of inertia of the boom joint arms with respect to the adjustable joints affect the adjustment characteristics of the joint to be adjusted.
An alternative to the experimental tuning of adjusters is to produce an accurate mathematical model on the system to be adjusted and to tune the joint controllers on the basis of the model. However, this poses a problem that the produced model would represent accurately just one particular boom and each boom model should be modelled separately. In practice, this is not economically feasible, if a simpler experimental solution is available.
Currently, boom adjustment control is tuned by performing calculation of approximate values of various parameters on the case of one degree of freedom, and subsequently, the joint controller parameters are tuned joint by joint using the method of trial and error, until the desired behaviour is achieved. If the tuners are ill-informed about adjustment techniques, it may be impossible, in practice, to feed numeral values to serve as joint controller parameters. Eventually, the end result of the adjustment will only be based on visual assessment if there is no suitable method and indicators for the assessment of the end result.